<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
		
		半径：<input type="text" placeholder="半径" id="a"/>
		周长：<input type="text" placeholder="周长" id="b"/>
		面积：<input type="text" placeholder="面积" id="c"/>
		<script type="text/javascript">
//			根据圆的半径
//			π * 半径的平方
			var p = Math.PI; //π
			var r = prompt('请输入圆的半径');
			var banJing = Math.pow(r,2);//计算平方
			var s = banJing * p;
			var z = 2 * p * r;
			var a = document.querySelector('#a').value = r;
			var b = document.querySelector('#b').value = s;
			var c = document.querySelector('#c').value = z;
		</script>
		
	</body>
</html>
